Taking a Look at Arthropods and Molluscs

A. Arthropods inherit many excellent synapse forms and unique features such as exoskeleton, molting and breathing. While these features of arthropod genetics open up many great opportunities for their evolution, they also hinder some possibilities and cause some difficulties. First, the exoskeleton of mink and arthropod seems to be a double-edged sword. The arthropod's rigid exoskeleton provides protection. This exoskeleton is also a basic building material of various tools such as attachments.

Two groups of invertebrates have a very complex brain. Arthropods (insects, crustaceans, spiders, etc.) and cephalopods (octopus, squid, and similar mollusks). Arthropods and cephalopods come from double parallel nerve cords that extend through the body of the animal. Arthropods have a central brain, upper esophageal ganglion, three sections behind each eye, and large optical lobes for visual processing. Cephalopods such as octopus and squid are the largest of all invertebrates

Cambrian age (541 - 485 Ma): The beginning of the Cambrian period was characterized by the Cambrian explosion and almost all invertebrate gates (arthropods such as molluscs, jellyfish, insects, crustaceans) suddenly Appears. The first vertebrate appeared in the form of untouched fish, and then diversified greatly in the Silurian and Devonian periods. Like Myllokunmingia and Haikouichthys ercaicunensis below, Pikaia is a candidate fossil record for the titles of "First Vertebrate" and "First Fish". Picaia is a genus of about 530 Ma that occurs during multivariate life of Cambrian. Pikaia gracilens (photo) is a transitional fossil between invertebrates and vertebrates, probably the earliest known chordate. In this sense, it may be the first ancestor of the fish. It is a primitive creature less than 2 inches (5 cm) in length without evidence of eye or clear head.